In a vehicle, absorbing and blocking sound is important. In order to prevent noise generated while driving a vehicle, various forms of sound absorbing and sound blocking members having excellent sound absorbing and sound blocking properties have been applied.
The sound absorbing property refers to a property of absorbing sound by an object or a porous material such as glass fiber or rock wool having numerous small holes therein, which has sufficient sound absorbing property. When a thin metal plate, plywood or the like is in close contact with a solid object, sound absorbing property is weak. However, an air layer as a sound spring created between a porous material and a solid object with a certain gap therebetween may absorb sound energy, thereby increasing sound absorbing property.
The sound blocking property refers to a property of blocking sound by an object. An object having no holes has sufficient sound blocking property which can be further enhanced by increasing the weight per unit area.
In order to manufacture a material with sound absorbing and sound blocking properties in the related art, a sound blocking layer is used, and a skin layer composed of a non-woven fabric and the like is added thereto. The material with sound absorbing and sound blocking properties has been manufactured by separately constituting a sound absorbing layer and attaching the sound absorbing layer to the sound blocking layer, which is a cumbersome process.
As social interests in the environment are increasing, and law and regulations regarding the environment become stricter, a technology reducing emission of environmental pollutants by recycling resources has been continuously developing.
Korean Patent No. 10-0246144 discloses a sound absorbing and sound blocking material obtained by recycling waste rubber. Adding calcium carbonate (CaCO3) and a hollow fiber into waste rubber have been introduced to improve insufficient sound blocking property and sound absorbing property. However, the process is cumbersome and complicated.